Hydrogel is a kind of polymer material with high water content and three dimensional crosslinked networks. Due to the excellent biocompatibility and mechanical strength, hydrogel can highly mimic biological tissue microenvironment. Therefore, it is widely used in tissue engineering and regenerative medicine, in which tissue repairment and isolation of clinical wound is an important category. Currently, the materials used in clinic wound tissue isolation and repairment mainly include solid membrane materials (Royce Johnson et al. U.S. Pat. No. 7,070,584 B2, issued Jul. 4, 2006), preformed colloidal materials (Yeong Hua Huang et al. U.S. Pat. No. 6,238,691 B1, issued May 29, 2001), and in situ gelling materials.
Of these materials, the solid membrane materials are inconvenient to use, as they are of high cost, difficult to attach to wounds, easy to fall off from the wounds, and requires additional immobilization. In addition, the application of the solid membrane materials are seriously impacted due to lack of biodegradability. Similar to solid membrane materials, preformed colloidal materials are gelled and shaped before applying to the wound, and thus they cannot completely match the surface of the wound, which results in uncomplete coverage of the wound tissue and in turn affects their effectiveness. Compared to the above two kinds of materials, the in situ gelling materials are cured in situ on the wound. The excellent shaping property of the in situ gelling materials allows the in situ gelling materials to match the surface of the wound completely. Therefore, a good attachment to wound tissue can be achieved, which ensures good fixation and avoids falling off easily. Currently, the materials applied in in situ wound tissue isolation and repair in the market mainly include mono-component thermosensitive gel (Paul A. Higham et. al. U.S. Pat. No. 5,093,319 A, issued Mar. 3, 1992) and two-component chemical crosslinking gel (Zalipsky et. al. U.S. Pat. No. 5,122,614, issued Jun. 16, 1992). Thermosensitive gel is difficult to store and the gel strength is relatively poor. Thus its adjustable range is very narrow. For two-component chemical crosslinking hydrogel, its gelling speed is faster and gel strength is larger. Therefore, the adjustable range of this hydrogel type is wider. However, the gelling time of this materials is not controllable and the operation is inconvenient. Moreover, the instruments for mixing two-component materials are very expensive, which greatly increases the cost. Therefore, the extensive application of this kind of materials is limited.
Photoinitiated gelling materials have received widespread attention because of the advantage of non-physical contact and accurate spatiotemporal controllability of light. Traditional free radical initiated photo-polymerization (Hubbell et al. U.S. Pat. No. 6,060,582 A, issued May 9, 2000) and thiol-ene reaction developed from free radical initiated photo-polymerization (Christopher Bowman et al. U.S. Pat. No. 7,288,608 B2, issued Oct. 30, 2007) are the typical representations of photogelling reaction. In these systems, the small molecular photoinitiator must be added. The small molecular photoinitiator can generate free radicals after illumination, which in turn have great side effects on cells or biological tissue. In addition, the small molecular photoinitiator is extremely sensitive to oxygen and is difficult to prepare relatively thin layer hydrogel. However, in wound tissue isolation and repair, thin layer coating is always needed. Therefore, the traditional free radical initiated photo-polymerization is difficult to be clinically applied in in situ gelling on wounds.
In order to overcome the shortcoming of current materials, a novel non-free radical photo-crosslinking method is provided for making hydrogel. This non-free radical photo-crosslinking method not only overcomes the defects of the toxicity of free radicals and the sensitivity to oxygen, but also exhibits the characteristics of spatiotemporal controllability, simple synthesis and so on.